Bare electronic chips typically need to be packaged in a package that provides an electric circuit to each electrical connection of the chip and to an external connector such as a pin or a ball. Typical is a pin-grid array package having relatively large pins on one side for external connections, and pads on an opposite side for connections to a ball-grid-array set of connections to the electronic chip (such as a processor or memory chip). Also typical is a ball-grid array package having relatively large balls (e.g., in a ball-grid array) with relatively large spacings on one side of the package for external connections, and small closely spaced pads on the same side for connections to a ball-grid-array set of connections to the electronic chip (such as a processor or memory chip).
Such a package typically has a non-conductive substrate (such as a plastic film or layer) with conductive traces (wires) on or in a surface of the substrate. Some packages include multiple chips, such as one or more logic or processor chips, and/or one or more memory chips, such as a FLASH-type reprogrammable non-volatile memory. Balls and/or pins are attached to the outside of the package, and one or more electronic chips are attached, for example, by also using ball-grid-array connection methods and/or flying-wire methods. Optionally, a cover or encapsulant is used to enclose the chip or chips.
One conventional way to make such a package is to start with a sheet or strip of non-conductive material such as Mylar film or a fiberglass reinforced epoxy substrate, then deposit a film of metal such as copper, then pattern and etch the metal to leave traces. Sometimes, through-hole vias connect traces on one side or internal layer to traces on the other side or another internal layer. The chips are then connected to pads on the traces and sometimes encapsulated to form the package. Such packaging typically has poor thermal conductivity.
Chips that run at extremely high frequencies, e.g., upwards of 40 gigahertz, also have constraints as to the type, thickness, spacing, and layout of traces required to provide adequate signal capability. Further, such chips typically need to be run at very low voltages (e.g., about one volt) and very high currents (e.g., one hundred amps), which must be provided in order to achieve the desired high frequencies.
What is needed is a simple, inexpensive, reliable method and apparatus to fabricate packages for electronic chips, so that the package provides high heat conductivity and dissipation, and high frequency response.